The document provides a comprehensive overview of internal combustion (IC) engines, including the differences between external and internal engines, their components, and operational principles. It details various types of IC engines, such as two-stroke, four-stroke, and six-stroke engines, explaining their operating cycles and efficiencies, as well as applications. Additionally, it covers the specifics of spark ignition (SI) and compression ignition (CI) engines and their corresponding features and cooling systems.

1. Complete guide to
IC Engines

2. 1. Introduction to IC Engines

3. Heat Engine
A heat engine is a device which transforms the Chemical Energy
of a FUEL into Thermal Energy and uses this energy to produce
Mechanical Work.

4. ● External combustion engine
● Internal combustion engine
It is classified into two types:

5. External combustion engine :
External combustion engine are those in which the combustion
takes place outside the engine, the products of combustion of air and
fuel transfer heat to a second fluid which is the working fluid of the
cycle.

6. Limitations of EC Engine:
● A steam engine is huge and heavy. Due to its big Boiler and Furnace.
● Steam Engine does not Start at once.
● It operates on low efficiency. (20%)
● These steam engines are unsafe to use, its boiler can burst due to excessive
steam pressure!
Due to these limitations the EC Engines are replace by IC Engines.

7. Internal combustion engine :
In this engine the combustion of air fuel mixture takes place inside
the cylinder and used as direct motive force.

9. ● These engines are compact in size.
● IC engine don’t require boiler.
● Higher efficiency about 35-40%.
● Very noisy operated Engines.
Features of IC Engine :

11. 2. Components of IC Engines

12. ● Cylinder block
● Cylinder Head
● Piston
● Cylinder
● Piston Rings
● Gudgeon Pin
● Connecting Rod
● Crankshaft
● Cam Shaft
● Cams
● Inlet & Exhaust valve
● Fuel Injector
● Spark Plug
● Crankcase
● Flywheel
Components of IC Engine

13. The cylinder block is the main supporting structure for the various components. The
cylinder of multi cylinder engine are cast in single unit called as Cylinder Block
➔ Material : Cast Iron, Aluminum alloy
◆ CI for diesel engines, that
produce stronger explosion.
◆ Al for gasoline engine that
produces soft explosion.
Cylinder Block

14. Cylinder Head
The top end of the cylinder is covered by cylinder head over which inlet and
exhaust valve, spark plug or injectors are mounted

15. Piston
● It is cylindrical component fitted into the cylinder forming the moving boundary
of combustion system.
● Transmit the force exerted by the burning of charge to the connecting rod
● It fits perfectly into the cylinder providing a gas-tight space with the piston ring
and lubricant.
➔ Material : aluminium alloy
◆ Light Weight
◆ Thermal Conductivity
◆ Good tensile strength

18. Cylinder
● It is the main part of the engine in which the piston reciprocate to and fro.
● It also acts in transferring the heat from:
○ combustion chamber to water jacket in liquid cooled engine.
○ Combustion chamber to fins in air cooled engine.
➔ Material : Cast Iron
◆ Good wear Resistance
◆ Good Damping behaviour
◆ High Thermal conductivity
◆ inexpensive

21. Piston Rings
● Piston rings, fitted into the slots around the piston, provides tight seal between
the piston and cylinder wall thus preventing the leakage of combustion gases.
● There are two types of rings:
○ Compression ring is upper ring of the piston which provides air tight seal to prevent
leakage of the burnt gases into the lower portion.
○ Oil ring is lower ring which provides effective seal to prevent leakage of the oil
into the engine cylinder.
➔ Material : Cast Iron, steel
alloys(coated or heat treated)
◆ High thermal conductivity
◆ Wear resistance

24. Connecting Rod
● It converts reciprocating motion of the piston into circular motion of the
crankshaft, in the working stroke.
● The smaller end of the connecting rod is connected with the piston by
gudgeon pin and bigger end of the connecting rod is connected with the
crank with crank pin.
➔ Material : Steel alloys(drop
forged), Titanium, Aluminum
◆ Lightweight, flexible (Al)
◆ High performance(Ti)

27. Gudgeon Pin
It forms the link between the small end of connecting rod and piston

28. Crankshaft
● It converts the reciprocating motion of the piston into the useful rotary motion
of output shaft with the help of connecting rod.
● In the crankshaft of single cylinder engine there are a pair of crank arms and a
balance weights. The balance weights are provided for static and dynamic
balancing of the rotatory system.
● The crankshaft is enclose in the crankcase
➔ Material: Medium carbon
steel alloy(0.25-0.45%C) -
Foging
◆ High fatigue strength
◆ Hardness

30. Cam Shaft
● The cam shaft and its associate parts control the opening and closing of two
valves. The associate parts are pushrod, rocker arms,valve spring and tappets.
● The shaft also provide the drive to the ignition system.
● The camshaft is driven by the crankshaft through timing chain or timing gears.
➔ Material : chilled cast iron(1% Cr),
Billet Steel.
◆ high volume production,
have good wear resistance.
◆ high quality camshaft or low
volume production

32. Cams
These are made as integral parts of the camshaft and are designed in such a way to
open the valves at the correct timings and to keep them open for necessary duration
Cams

33. Inlet and exhaust valves
● Valves are commonly mushroom shape poppet type
● They are provided on the cylinder head for regulating the charge coming into
the cylinder(inlet valve) and for discharging the products of combustion
(exhaust valve) from the cylinder.
➔ Material: Stainless steel,
Titanium, Inconel,
◆ high
temperature,oxidation
,corrosion resistant

37. Spark Plug
● It is a component to initiate the combustion process in spark ignition(SI) engines
and is usually located on the cylinder head.

38. Fuel Injector
● It is a component to initiate the combustion process in compression ignition(CI)
engines and is usually located on the cylinder head.

40. CrankCase
● It is the bottom part of the Engine block
● It hose the crankshaft of the IC Engine and also serve as the sump for the
lubricating oil.

41. Flywheel
● It is big wheel mounted on the crankshaft, whose function is to maintain
its speed constant. It is done by storing excess energy during the power
stroke, which is returned during other stroke.
➔ Material : Cast iron,
Steel, (Dense Material)

42. 3.Two Stroke Engine

43. (i) Compression stroke:
❖ When piston is at BDC, the charge enters into
the cylinder through transfer port from
crankcase.
❖ When piston moves from BDC to TDC, the
charge is compressed in the cylinder and along
with that the fresh charge is induced into the
crankcase through the spring loaded inlet valve
due to pressure difference.
Simple Two stroke EngineSimple Two stroke Engine

44. (ii) Expansion stroke:
At the end of compression stroke the spark plug actuates
and combustion takes place, piston moves from TDC to
BDC
❖ During the expansion stroke the fresh charge is partially
compressed in crankcase.
❖ Near the end of expansion stroke the piston uncovers the
exhaust port and combustion products leaves the
cylinder to atmospheric pressure.
❖ Further moment of piston uncovers the transfer port,
permitting the slightly compressed charge in crankcase to
enter the cylinder.

45. ➔ The top of the piston has usually a projection to deflect the fresh charge towards the
top of cylinder before flowing to the exhaust port. It serves the double purpose:
● Scavenging the upper part of cylinder of the combustion products
● Preventing the fresh charge from flowing directly to exhaust ports
➔ The same
objective can be
achieved without
piston deflector
by proper shaping
of transfer port.

46. Two stroke Engine
❖ In two stroke engine the cycle is completed in one revolution of crankshaft
❖ The main difference is in the method of filling the fresh charge and removing the burnt gases
from the cylinder
❖ In two stroke the filling process is accomplished by charge compressed in crankcase.
❖ The induction of compressed charge moves out combustion products through exhaust port.
❖ Therefore no piston strokes required for suction and exhaust operation.
❖ Two strokes are sufficient to complete the cycle one for compressing the fresh charge and
other for expansion or power stroke.

47. Four Stroke Engine
● Thermodynamic cycle is completed in
Four stroke of the piston and two
revolution of crankshaft
● One power stroke in every two revolution
of crankshaft
● Heavier flywheel due to non uniform
turning movement.
● Power produce is less
● Heavy and bulky
● Lesser cooling and lubrication
requirements
● Lesser rate of wear and tear
● Thermodynamic cycle is completed in
Two stroke of the piston and one
revolution of crankshaft
● One power stroke in each revolution of
crankshaft
● Lighter flywheel due to more uniform
turning movement
● Theoretically power produce is twice
than the four stroke engine for same
size.(30%)
● Light and compact
● Greater cooling and lubrication
requirements
● Higher rate of wear and tear
vs Two Stroke Engine

48. ● Contains valve and valve mechanism
● Higher initial cost
● Volumetric efficiency is more due to
greater time of induction
● Thermal efficiency is high and also part
load efficiency better
● It is used where efficiency is important.
Ex-cars, buses, trucks, tractors, industrial
engines, power generation etc
● Contains ports arrangement
● Cheaper initial cost
● Volumetric efficiency less due to lesser
time of induction
● Thermal efficiency is low, part load
efficiency lesser
● It is used where low cost, compactness
and light weight are important.
Ex-lawn mowers, scooters, motorcycles,
mopeds, propulsion ship etc.

49. Applications of Two Stroke Engine:

50. Automobile

51. Farm Applications:

53. Marine Engines

56. 4. Four Stroke SI Engine

57. Four Stroke SI Engine
● The cycle of operation is completed in four strokes of the piston or the two
revolutions of crankshaft
● There are five events to be completed , suction, compression, combustion,
expansion and exhaust.
● Each stroke is 180°crankshaft revolution and hence a Four stroke is
720°crankshaft revolution
● Cycle of operation:
○ Suction or Intake Stroke
○ Compression stroke
○ Expansion or power stroke
○ Exhaust stroke

59. ➢ Starts when piston is at TDC and about to move
downwards
➢ The inlet valve is opened at this time and
exhaust valve is closed
➢ Due to the suction created by the motion of
piston towards BDC the charge consisting of air-
fuel mixture is drawn into the cylinder
➢ When piston reaches the the BDC the suction
stroke ends and the inlet valve closes
(i) Suction or Intake stroke:

60. ➢ The charge taken into the cylinder during the suction
stroke is compressed by return stroke of piston
➢ During this stroke Inlet and exhaust valve are in
closed position
➢ The mixter which fills the entire cylinder volume is
now compressed.
➢ At the end of compression stroke the mixture is
ignited with the help of spark plug located on the
cylinder head and hence burning takes place
instantaneously
➢ The chemical energy of fuel is converted into heat
energy producing temp rise of about 2000°C
(ii) Compression stroke:

61. ➢ The high pressure of burnt gases forces the
piston towards BDC
➢ During this stroke Both the valves are in closed
position
➢ Of the four strokes only during this stroke the
power is produced
➢ Both pressure and temperature decreases
during expansion.
(iii) Expansion Or Power Stroke:

62. ➢ At the end of expansion stroke the exhaust
valve opens and the inlet valve remains
closed
➢ The piston starts moving from BDC to TDC
and sweeps the burnt gases out from the
cylinder almost at atm pressure.
➢ The exhaust valve closes when the piston
reaches the TDC.
(iv) Exhaust stroke:

63. Four stroke engine completes the above four operation in two engine
revolutions
➔ One revolution of crankshaft occurs during suction & compression
stroke
➔ And Second revolution during the power & exhaust stroke
Thus in one complete cycle there is only one power stroke while the
crankshaft turns by two revolution

64. Four Stroke CI Engine
The four stroke CI Engine is similar to four stroke SI engine but it operates
at a much higher compression ratio.
Compression Ratio: In SI engine is “6 to 10”
In CI engine is “16 to 20”
Due to the high compression ratio temperature at the end of compression
stroke is sufficiently high to self ignite the fuel.

65. (i)Suction stroke:
Air alone is induced during the suction stroke
During this stroke inlet valve is opened and
exhaust valve is closed
(ii)Compression stroke:
Air induced during the suction stroke is
compressed into clearance volume
Both valves remains closed during this stroke

66. (iii)Expansion stroke:
Fuel injection starts nearly at the end of the
compression stroke
After injection of the fuel is completed the product
of combustion expand
Both valve remains closed during the expansion
stroke
(iv)Exhaust stroke:
Piston travelling from BDC to TDC pushes out the
product of combustion
The exhaust valve is opened and inlet valve is
closed during this stroke

67. Applications of 4 stroke engine:

69. Locomotives:

70. Small propeller Aircrafts
Lycoming IO-360-A1B6

71. Small outboard motor

72. Power Generation

73. 5.Six stroke Engine

74. Six stroke Engine
● In six stroke engine the thermodynamic cycle is completed in 3
revolution of crankshaft.
● The main difference is the addition of two extra strokes i.e.,
2nd power stroke and exhaust stroke.
● The engine captures the exhausted heat from the four stroke
cycle and uses it to get an additional power of the piston in the
same cylinder.

75. Velozeta six-stroke engine
In a Velozeta engine, fresh air is injected into the cylinder during the exhaust
stroke, which expands by heat and therefore forces the piston down for an
additional stroke. The two additional strokes using air injection provide for
better gas scavenging. The engine seems to show 40% reduction in fuel
consumption and dramatic reduction in air pollution.Its Power-to-weight ratio is
slightly less than that of a four-stroke gasoline engine. The engine was
developed in 2005 by a team of mechanical engineering students from kerala.

76. Crower six-stroke engine
This six-stroke engine prototyped in the United States by Bruce Crower, water
is injected into the cylinder after the exhaust stroke and is instantly turned to
steam, which expands and forces the piston down for an additional power
stroke.Crower estimated that his design would reduce fuel consumption by 40%
by generating the same power output at a lower rotational speed.

77. Working:
● The first four stroke are same as that of four stroke engine
● Suction stroke : charge is sucked into the cylinder, piston moves from TDC to
BDC.Inlet valve remains open during this stroke
● Compression stroke : air fuel mixture or charge is compressed in the cylinder,
piston moves from BDC to TDC. Both the valves remains closed. At the end of
compression stroke the air fuel mixture is ignited with the help of spark plug
and burning of gases takes place.
● Expansion or powerstroke : The high pressure gases forces the piston down to
BDC. during this stroke both the valves remains closed. This is the first power
stroke produced in cycle with the help of fuel.

78. ● Exhaust stroke : at the end of expansion stroke the exhaust valve opens and inlet
valve remains closed. The piston will exhale the burnt gases out of the cylinder.
● 2nd power stroke :
○ the fresh air from air filter enters the cylinder through the secondary air
induction line.(velozeta)
○ The water is injected in the super heated cylinder. Through hot gases the water
changes its phase into steam as the temperature of hot gases is high. This steam
will act as a working fluid and forces the piston downwards. (crower)
● 2nd Exhaust stroke : during the sixth stroke the exhaust valve remains open. The
piston discharges the gases out of the cylinder.
Working:

79. Velozeta six-stroke engine e e

80. Crower six-stroke engine e

81. Features of six stroke engine:
● The efforts in cooling the engine is considerably reduced and makes the engine lighter.
● Six stroke engine seems to show 40% reduction in fuel consumption.
● This engine shows around 60% reduction in carbon monoxide pollution when
compared to four stroke gasoline engine.

82. 6. Spark Ignition Engine
or
Gasoline(Petrol) Engine

83. ❖ 0 → 1 :Suction Stroke
❖ 1 → 2 : Compression stroke
❖ 2 → 3 : Constant volume Heat Addition
❖ 3 → 4: Expansion stroke
❖ 4 → 5 : Const vol Heat Rejection.
❖ 5 → 0 : Exhaust stroke
SI Engine Works on Otto Cycle

84. ● Basic Cycle:
○ Works on Otto cycle or constant volume heat addition cycle.
● Fuel:
○ Gasoline, a highly volatile fuel. Self ignition temperature is high i.e.,280°C
whereas for diesel it is 210°C.
● Introduction of fuel:
○ A gaseous mixture of air-fuel is introduced during the suction stroke.
○ Carburetor and ignition system are necessary
● Load Control:
○ Throttle controls the quantity of fuel air mixture introduced.
Features of SI Engine

85. ● Ignition:
○ Requires Ignition system with spark plug in the combustion chamber. Primary
voltage is provided by a battery.
● Compression Ratio:
○ 6-10 upper limit is fixed by antiknock quality of fuel.
● Speed:
○ Due to light weight and also due to homogeneous combustion, they are high
speed engines.
● Thermal Efficiency:
○ Because of low compression ratio the maximum value of thermal efficiency
that can be obtained is lower

86. ● Weight:
○ Lighter due to lower peak pressure.

87. 7. Compression Ignition Engine
or
Diesel Engine

88. CI engine works on Diesel Cycle
❖ 0 → 1 :Suction Stroke
❖ 1 → 2 : Compression stroke
❖ 2 → 3 : Constant pressure Heat
Addition
❖ 3 → 4: Expansion stroke
❖ 4 → 5 : Constant volume Heat
Rejection.
❖ 5 → 0 : Exhaust stroke

89. ➔ Basic Cycle:
◆ Works on diesel cycle or constant pressure heat addition cycle.
➔ Fuel:
◆ Diesel oil a non-volatile fuel. Self ignition temperature is comparatively low.
➔ Introduction of fuel:
◆ Fuel is injected directly into the combustion chamber at the high pressure at
the end
of compression stroke.
◆ A fuel pump and injector are necessary.
Features of CI Engine

90. ➔ Load Control:
◆ The quality of fuel is regulated. Air quantity is not controlled.
➔ Ignition:
◆ Self ignition occurs due to high temperature of air because of high
compression.
◆ Ignition system and spark plug are not necessary.
➔ Compression Ratio:
◆ 16-20 upper limit is limited by weight increase of engine
➔ Speed:
◆ Due to heavy weight and also due to heterogeneous combustion, they are
low speed engines.

91. ➔ Thermal Efficiency:
◆ Because of higher compression ratio the maximum value of thermal efficiency
that can be obtained is higher.
➔ Weight:
◆ Heavier due to higher peak pressure.

92. 8. Engine Cooling System

93. ➔ All heat produced by combustion of fuel is not converted into useful work at
crankshaft. A typical distribution for the fuel energy is given below:
◆ Useful work at crankshaft = 25%
◆ Loss to the cylinder wall = 30%
◆ Loss to exhaust gases = 35%
◆ Loss in friction = 10%
➔ The quantity of heat given to cylinder wall is considerable and if this heat is not
removed from cylinders it would result in pre ignition of charge, burnt away the
lubricant and damages the cylinder material.
➔ So it is necessary to dissipate the excess heat from the cylinder walls.

94. Methods of Engine cooling
1. Air cooling 2. Water cooling

95. Air Cooling
● Surface area of metal in contact with air
● Mass flow rate of air
● Temperature difference between the
heated surface and air
● Conductivity of metal
Thus for effective cooling surface area of
metal in contact with air should be increased.
This is done by providing fins over cylinder
barrel.
The basic principle involved in this method is to have current of air flowing
continuously over the heated metal surface. It depends on following factors:

96. Features
:★ Air cooled engine are lighter because of absence of radiator, cooling jacket
and the coolant.
★ Can be operated in extreme climate.
★ Maintenance is easier because no problem of leakage.
★ Gets easily warmup than water cooled engine.
★ Not easy to maintain even cooling around cylinder.
★ The cooling fins may vibrate due to which noise levels may increase

97. Water Cooling
The cooling medium used is water. The engine cylinder are surrounded by water
jackets through which cooling water flows.
Heat flows from cylinder walls to water which goes to the radiator where it loses its
heat to surrounding.
Usually some antifreeze is added to cooling water due to which it is often referred as
coolant.

99. ➢ Circulating liquid gets the heat from engine cylinder,thereby cooling the same.
➢ The same heat in the liquid is then dissipated into the atmosphere through the
radiator, by mainly conduction and convection.
➢ Circulating liquid gets cooled by the time it reaches the collector tank of the
radiator.
➢ The same water is then circulated through the engine to collect the heat from the
cylinders.
➢ The pump is used for the circulation and thermostat is employed to control the
flow of coolant.
➢ The pump is driven by means of belt from engine crankshaft, the drive for fan is
also obtained from the same belt

100. Features
:★ Employed in both medium and heavy load applications like cars, truck,
buses,etc.
★ Easy to maintain even cooling around the cylinder.
★ Circulation of coolant is proportional to both load and speed.
★ More complicated and costlier than air cooling system.

102. 9. IC Engine Lubrication system

103. Lubrication
● Lubrication is a process of admitting oil between two surfaces which are in
direct contact.
● The engine can not run smoothly for more than few minutes without
lubricating oil.
● Whenever two metallic surfaces move over each other under direct contact,
dry or solid friction is produced. This is due to irregularities on two surfaces
interlocking each other.
● The dry friction thus created produces a lot of heat and results in wear and tear
of the metal surface

104. ● When a film of some lubricating oil is interposed between two surfaces so that
the two are not in actual physical contact with each other, the only resistance to
motion remains the resistance of oil itself. This type of friction is termed as
viscous or fluid friction.
Lubrication

105. ● Primary objectives:
○ To reduce the friction between moving parts to its minimum value so that
power loss is minimised.
○ To reduce wear of the moving parts as far as possible
● Secondary objectives:
○ To provide cooling effect: The lubricating oil takes the heat from hot moving
parts.
○ To provide cushioning effect: The lubricating oil serves also as a good
cushion against the shocks present in the engine.
Objectives of Lubrication

106. ○ To provide cleaning action: During its circulation it dissolves many
impurities e.g., carbon particles. This oil may be purified by filtration.
○ To provide a sealing action: lubricating oil also helps the piston rings to
maintain an effective seal against the high pressure gases in the cylinder
from leaking out toward the crank side.

108. ● Viscosity:
○ Viscosity is the resistance of the lubricating oil to flow.
○ Viscosity should be just sufficient to ensure the hydrodynamic lubrication.
Higher the value results in higher the power loss due to increased oil
resistance. At the time of starting the engine viscosity should be low
otherwise, the engine may not start.
● Physical stability:
○ The lubricating oil must be stable physically at lowest and highest
temperature encounter.
○ There should not be any separation of solids at lower temperature and at
higher temperature it should not vapourised.
Requirements of lubricant

109. ● Chemical Stability:
○ At higher temperature the oil should remain chemically stable. There
should not be any tendency for oxide formation (sticky substances).
● Resistance against corrosion:
○ The oil should not have any tendency to corrode the pipeline, crankcase
and other engine parts with which it comes in contact.
● Flash point:
○ The flash point of oil should be sufficiently high so as to avoid flashing of
oil vapours at the temperature occurring in common use.
● Cleanliness:
○ The oil should be sufficiently clean and stable itself so that the crankcase
and oil liners are kept clean.
○ Further it must contain agents called detergents which removes the
impurities during circulation.
Requirements of lubricant

110. Types of lubrication system
The lubrication system is classified into
1. Petroil lubrication system.
2. Wet sump lubrication.

111. 1.Petroil lubrication system
● This is used generally for small two stroke engines such as scooter and
motorcycle engines. Certain amount of lubricating oil is mixed with petrol itself.
The usual ratio is 2% to 3% of oil.
● If it is less, there is danger of insufficient lubrication causing damage to the
engine. If it is more, there will be excessive carbon deposits and the engine will
also give dark smoke.
● Piston rings and cylinder walls and gudgeon pin bearings are lubricated by this
method.
● The fuel-oil ratio used is important for good performance. the optimum fuel-oil
ratio used is 50:1.

113. Wet Sump lubrication
In this system a big oil sump is provided at the base of crankcase.From
the sump the oil is pumped to different parts of the engine.The main
types of wet sump lubrication system are
1. splash lubrication system.
2. Pressure lubrication system.

114. ● This is generally employed for small, low duty
engines. This is one of the cheapest methods of
engine lubrication.
● A scoop s made in the lower part of the
connecting rod and oil is stored in the oil
troughs or crankcase.
● When the engine runs, once in every
revolution, the scoop causes the oil to splash
on all directions.
● This effects the lubrication of cylinder walls,
gudgeon pin, crankshaft main bearings, big end
bearings, piston, valve, timing gears and cams.
Splash system

115. Pressure system
➔ In the pressure system, an oil pump takes the oil from the sump through a strainer and
delivers it through a filter to the main oil gallery at a pressure of 2 to 4 bar.
➔ From the main gallery, the oil goes to the main bearings. From here, some of the oil after
lubrication falls back to the sump, some is splashed to lubricate cylinder walls and the rest
goes through a hole to the crank pins for lubricating big end bearings.
➔ A hole in the connecting rod web, leads the oil from crank pin hole to the gudgeon pin.
After lubricating gudgeon pin bearings, the oil falls back.
➔ For the camshaft and timing gear, lubricating oil is led through the separate oil line from the
oil gallery through a pressure reducing valve.
➔ To lubricate timing gears, sometimes an oil jet is directed to these parts. The valve tappets
are lubricated by connecting the main oil gallery to the tappet guide surfaces through
drilled holes

116. Parts of an engine to be lubricated
The main parts of an engine which requires lubrication are:
1. Main crankshaft bearings.
2. Big end and small end bearings of connecting rod.
3. Gudgeon pin bearings.
4. Timing gears.
5. Camshaft and camshaft bearings.
6. Piston rings and cylinder walls.
7. Valve mechanism.

120. 10. Technological Advancements in
IC Engine

121. i-VTEC Engine
● i-VTEC (Intelligent Variable Valve Timing & Lift Electronic Control) is a system
developed by Honda which was said to improve the volumetric efficiency of a
four-stroke internal combustion engine.
● Resulting in higher performance at high RPM, and lower fuel consumption at
low RPM. The VTEC system uses three camshaft profiles and hydraulically
selects between profiles.
● It was invented by Honda engineer Ikuo Kajitani.

122. i-VTEC: high power and low fuel consumption
● control openings of two intake valves
○ i-VTEC regulates the opening of air-fuel intake valves and exhaust valves
in accordance with engine speeds.
○ opening a small amount at low engine speeds and fully opening at high
engines speeds, achieving both high power and low fuel consumption
● Idling one intake valve
○ The new i-VTEC engine is agile and intelligent: at low engine speeds one
of the two intake valves is idled. The engine sips gasoline, using a lean
fuel mix at low engine speeds for further improved combustion efficiency.

124. CRDI Engine
● Most modern engine's fuel systems use an advanced technology known as CRDi or
Common Rail Direct Injection.
● Both petrol and diesel engines use a common 'fuel-rail' which supplies the fuel to
injectors. However, in diesel engines, manufacturers refer to this technology as CRDi
whereas Petrol engines term it as Gasoline Direct Injection (GDI) .
● Direct injection of the fuel into the cylinders of a engine via a single common line called
the common rail which is connected to all the fuel injectors.
● Instead of providing separate pumps for fuel supply. The common rail alone supplies high
pressure fuel to each cylinder.
● This allows fuel to combine with air much more efficiently.

125. ● CRDI ensures the fuel injection timing, quantity of fuel and atomisation of fuel
spray are controlled electronically using a programmable control module.
● This allows multiple injections at any pressure at any time (within predefined
limits), providing a level of flexibility which can be exploited for better power,
fuel consumption and emission control.
● The electronic control and multiple injection reduced the noise to great extent.
● Ultra high pressure crdi (1800 bar) generating the ideal swirl and allowing the
air-fuel mixture to form uniform combustion and greatly reduced NOx emissions
CRDI Engine

128. ● It is basically a design optimization in the engine, which induces a
swirling or spinning motion in the air-fuel mixture as it enters the
combustion chamber.
● The swirling motion aids in better mixing of the fuel particles with air.
● The advantage of this technology is a more efficient combustion of
fuel, resulting in better fuel economy and cleaner emissions.
ATFT- (Advanced Tumble Flow Technology)

129. Features of ATFT:
● Tumble flow also indicates that the air-flow circulating in the direction of the
cylinder axis. Thus, it is beneficial in homogenizing the air-fuel mixture.
● It also has little effect on accelerating the combustion process by generating
turbulence. So, the tumble flow effectively improves the engine combustion at
light load when it completes near the end of the compression stroke.
● Hero Motocorp offers the ATFT technology on its CBZ Xtreme, Hunk and
Achiever models.

131. Resources-
IC Engines online course
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